OK, I'm the guy that was having the same problem, but had a blue tint to the screen. I also had blue lines running across the screen, and when I followed the steps below that were posted by another user not only did the lines disappear, but the blue haze vanished as well. My tv looks like it's new again, so you may want to try this:
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I have fixed this several times on my KP 65WV700
As Slinteriors posted if it is a thin curved line you need to adjust the screen control, it's sorta like a brightness for each color, and if one color is too high it will produce a thin curved line.
The best way I have found to get to the controls is by removing the lower grey speaker cover front the front of the TV. There are 6 screws if i remember, 3 on each side. Then it snaps off, seems like its going to break but you have to pop it off pretty good.
Once its loose you have to remove a cardboard like cover plate in the center that will give you access to the small controller board.
Now be very careful while experimenting on which knob controls which colors. Turn them very slow, if you turn to fast you will cause your TV to shut down. If this happens, turn the adjustment back to original spot and turn TV back on and take it slow.
Adjust the correct color until the line just goes away. Its easiest to do this with a black screen.